System and method for time-space-position-information (TSPI)

ABSTRACT

A system and method for time-space-position-information (TSPI) includes at least one air-based platform having an on-board navigation system. The on-board navigation system includes a dedicated on-board transmitter and a dedicated on-board receiver. A plurality of ground-based receiver nodes are in communication with the on-board transmitter of the air-based platform. A plurality of ground-based pseudolite transmitter nodes are in communication with the on-board receiver of the air-based platform. The system can provide TSPI solutions for the air-based platform during range and field testing. A ground-based station controls and monitors system components and processes data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a non-provisional application, claiming the benefit of parentprovisional application No. 61/757,370 filed on Jan. 28, 2013, wherebythe entire disclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

The invention generally relates to advanced range instrumentationtechnology systems, and more particularly, to a new system and methodfor providing precise time-space-position-information (TSPI).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system and its operational components for providingtime-space-information, according to some embodiments of the invention.

FIG. 2 is an exemplary block process diagram/flowchart of providingtime-space-position-information, according to some embodiments of theinvention.

FIG. 3 is an exemplary block process diagram/flowchart of providingtime-space-position-information, according to some embodiments of theinvention.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the invention, as claimed.Further advantages of this invention will be apparent after a review ofthe following detailed description of the disclosed embodiments, whichare illustrated schematically in the accompanying drawings and in theappended claims.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention generally relates to a new system and method for providingprecise time-space-position-information (TSPI). Embodiments of theinvention provide the Navy with a novel approach for TSPI in severalareas including, but not limited to, global positioning systems (GPS)denied environments, highly dynamic aircraft, Unmanned Air Vehicles(UAVs), and highly-dynamic guided weapons.

Embodiments of the invention include robust, a lowcost-size-weight-and-power (c-SWAP) GPS/INS navigation and timing systemon-board the air vehicle. Other instruments are also included such as,for example, altimeters, precise frequency sources and clocks, and alow-power transmitter on-board the air vehicle that provides a wirelessdata link of the TSPI information to the ground. Other on-boardcomponents can also include image-based navigation systems. Embodimentsenable more versatile and lower cost range instrumentation and flighttest capabilities compared to the use of traditional large ground basedassets like radar. Embodiments provide a small, robust, rapidlydeployable high-performance TSPI system for use on-board air vehiclesand components involving low-cost ground networks. Reduction in totaloperating costs for range tests involving small air vehicles isexpected.

Embodiments of the invention offer a new advanced range instrumentationtechnology (AIST) system for providing precise TSPI. Systems thatprovide TSPI are used in U.S. Department of Defense (DoD) ranges fordevelopmental testing of new sensor systems, testing the positioning,navigation, and timing (PNT) performance of navigation systems, guidanceand targeting systems, usually for aircraft and other airborne systems,such as manned and unmanned air vehicles (UAVs), precision guidedmunitions, and aerostats. PNT is sometimes also referred to inconjunction with position, velocity, and time (PVT). Embodiments of theinvention may also be equally applied to larger, less dynamic aircraft.

Traditional TSPI systems include on-board GPS and GPS/inertialnavigation system (INS) and other navigation sensor combinations andground-based systems such as radar and high precision photometry, suchas using cinetheodolites. For on-board systems using GPS often the TSPIor measurement information captured on-board is telemetered to theground using a wireless data link to provide real-time TSPI forreal-time performance evaluation and range safety or flight safetyapplications involving multiple air vehicles. The TSPI data may also besaved on-board the vehicle and later post processed when the flight testis complete.

Traditional ground-based TSPI systems, including high-performance radarand high-precision photometry systems such as using cinetheodolites, cantrack air vehicles to provide TSPI solutions independent of on-boardnavigation systems. However, the traditional systems tend to be largeand expensive to maintain and expensive to operate for range testing.Data from on-board systems, for example a GPS/INS/TSPI system on-boardan air vehicle, may be combined with data from ground-based systems toprovide more robust and precise capabilities. Techniques for fusing dataand other approaches for enabling improved on-board TSPI involve theinclusion of other types of sensors and information for navigation andtiming such as, for example, geo-referenced imagery database informationand images captured by imaging sensors, signals of opportunity, radar,precise frequency sources and clocks and other systems and sensors.

More generally, embodiments of the invention also apply for use as aTSPI truth source for range testing (also known as flight testing) theperformance of any platform primary navigation system which uses GlobalNavigation Satellite Systems (GNSS), which includes GPS and also foreignnavigation satellite systems. For embodiments of the invention, the useof “GPS” is equivalent to GNSS. Embodiments of the invention offer anindependent truth source that may be compared to the PNT solution beingproduced by the air vehicle's integrated navigation system forperformance testing. The platform navigation system is permanentlyintegrated into the air vehicle, whereas the TSPI truth reference isonly used to provide an independent reference for flight testing. Theassumption is that the TSPI truth source is more accurate and morerobust than the system being tested. Having multiple, independent TSPIsources is often important for range safety applications for improvedavailability and integrity, in the event one TSPI source is notavailable, or for cross checking independent sources of information.

Embodiments of the invention offer collaborative signal processing usinga network of ground receivers. Some novel aspects are related to theTSPI application. This includes the addition of the mission planningfeature at the ground station. Embodied in this approach is thepre-planning deployment of the ground network and also to remotelydistribute initialization and configuration data to/from (and between)the air based and ground based network of receivers and transmitters.This includes assigning air vehicle ID numbers and vehicle and groundpseudolite pseudorandom code (PRN) numbers/IDs, nominal flighttrajectory information, time synch, TSPI type, signal processinginformation and data relay control approach. Likewise, the use ofmultiple data link channels for robustness is included. Examples includeusing this technique in the presence of RF interference or jamming, whenGPS or other signals may not be available or reliable, as well as duringautomatic interference monitoring and reconfiguration control such as,for example, switching to GPS-denied test operation configuration or toa new wireless data link frequency.

Although embodiments of the invention are described in considerabledetail, including references to certain versions thereof, other versionsare possible. Examples of other versions include performing the tasks inan alternate sequence or hosting embodiments on different platforms.Therefore, the spirit and scope of the appended claims should not belimited to the description of versions included herein.

At the outset, it is helpful to describe various conventions andparameters associated with embodiments of the invention. This includesdefinitions, the operating environment, and the designation of certaincomponents included in embodiments of the invention.

TERMS/DEFINITIONS THE ART

The phrase “TSPI data” is used throughout. Many different forms of TSPIdata exist. Some examples of TSPI data as referred to in embodiments ofthe invention include, but are not limited to, the kinematical data, orthe sensor measurement data from which kinematical data is computed.Examples include OPS and INS sensor measurements data, vehicle position,velocity, acceleration and attitude data as a function of time asmeasured or computed by the navigation system on-board the air platformsor the emitter geolocation data obtained by tracking the wireless datalink. TSPI data usually refers to the position, velocity, acceleration,roll, pitch, and yaw as functions of time. However, for embodiments ofthe invention, raw sensor measurements can also be relayed to the groundand the TSPI solution can be computed on the ground in a processingstation. Other important information not traditionally described as TSPIdata includes component health data, and status data of components orthe mission.

The phrase “TSPI solutions” is also used throughout. In general, TSPIsolutions may be thought of as the processed TSPI data including, butnot limited to, kinematical information of the vehicle as a function oftime such as, for example, position, velocity, acceleration and attitudeinformation. The TSPI solutions may be computed differently depending oncomponent configurations dictated by field conditions. The TSPI data orTSPI solutions as defined above, generically describe or are used toevaluate the position, navigation, and timing (PNT) performance ofon-board navigation systems disclosed herein. Reference character 104(shown in FIG. 1) is used to depict an onboard-navigation system thatprovides TSPI data or TSPI solutions.

For range or flight testing applications, the navigation system depictedin character 104 may be an additional component that is deployed on anair platform (reference character 102) during a flight test to providean independent TSPI reference to assess the performance of otherinstruments and systems on-board the air platform. However, thenavigation system associated with character 104 is typically notdeployed in the air platform during operational use. For example, theon-board navigation system which provides TSPI may represent a highperformance navigation system that is only deployed during the flighttest to assess the performance of another navigation system that ispermanently integrated into the air platform for operational use.Embodiments are disclosed where the TSPI solutions are computed in theon-board navigation system 104. Additionally, the system includes aground-based station 112 (shown in FIG. 1), which may also be used tocompute TSPI solutions.

“Precise” GPS satellite ephemeris and clock information is a well-knownterm within the GPS community. It refers to more timely and accuratesatellite ephemeris and satellite clock data than what is availabledirectly from the Global Navigation Satellite Systems Space Vehicles(GNSS SV) broadcast signals. The “precise” data may be obtained viaconnection with the internet or a global information grid (GIG) (shownas reference character 120). The data may also be obtained via a networkconnection to a GPS Master Control Station.

When the precise data is available on-board, then more precise TSPInavigation solutions may be computed on-board the air platform ascompared to those solutions computed using the ephemeris and clock datain the GNSS broadcast signals. Alternatively, the on-board navigationsystem 104 can make navigation sensor measurements, relay themeasurements down to the ground-based station 112, and the ground-basedstation can incorporate the precise ephemeris and clock data as part ofthe TSPI solution.

The term “pseudolite” is used to describe a transmitter that createslocal, ground-based GPS-like signals. Hence, the term “pseudolitetransmitter” (or similar) is generally used herein and in the figures(FIG. 1, reference character 110) to describe a ground-based transmittertransmitting GPS-like or GPS-alternative signals. The pseudolitefunctions differently than a traditional wireless communicationstransmitter used to send wireless messages to a receiver, in that thepseudolite uses navigation signals to send these messages. Thus, areceiver that tracks the pseudolite signals can receive messages, butcan also use the pseudolite signals for navigation just like a GPSreceiver uses GPS satellite signals for navigation. GPS andpseudolite-based navigation systems may also be designed so that thereceivers can track both the signals broadcast from GPS satellites aswell as the signals transmitted from the pseduolites and use both setsof signals to compute TSPI solutions, or switch from GPS satellitesignals to pseudolite signals for TSPI when GPS signals are notavailable such as, for example, during range tests involving GPSjamming. While pseudolites are usually ground-based, as with the otherdiscussed components, the pseudolite transmitters 110 may also belocated away from land, such as, for example, in sea or littoralregions, without loss of generality. Ground based pseudolites at fixedsurveyed locations generally represent the most practical approach forrange or flight testing applications.

The phrase “data stripping” refers to a GPS signal processing techniqueto provide increased processing gain such as, for example, to increasesignal sensitivity or jam-resistance. With data stripping, thenavigation message data bits are either predicted or provided in advanceto the receiver. The receiver adjusts the carrier phase at data bittransition epochs according to the known data bit modulation to extendthe coherent integration time interval.

Operating Environment

In the accompanying drawings, like reference numbers indicate likeelements. FIG. 1 illustrates a system, depicted as reference character100, and the operational components for determiningtime-space-position-information (abbreviated as TSPI), according to someembodiments of the invention. The TSPI determination involves signaltransmission, reception and processing. All signals discussed throughoutare non-transitory.

Embodiments of the invention generally relate to a system 100 fordetermining time-space-position-information of an air-based platform.The system 100 includes at least one air-based platform 102. Severaltypes of platforms may be used for the air-based platforms 102 withoutdetracting from the merits or generality of embodiments of theinvention. Air-based platforms 102 may be manned, unmanned, or acombination of both, depending on mission or testing environments.Air-based platform options include, but are not limited to, airvehicles, aerostats, and precision guided munitions. Embodiments of theinvention are also applicable to rockets and space vehicles.

The air-based platforms have an on-board navigation system, genericallyshown as reference character 104. A dedicated on-board receiver(abbreviated as “Rec”) 104A and a dedicated on-board transmitter(abbreviated as “Xmit”) 104B are also included. The dedicated on-boardreceiver 104A is typically considered to be part of the on-boardnavigation system 104, whereas the dedicated on-board transmitter 104Bis typically not included as part of the on-board navigation system. Aninertial navigation system (abbreviated as “INS”) 104C is integratedwith the dedicated on-board receiver 104B in some embodiments. For easeof illustration, the on-board navigation system 104, dedicated on-boardreceiver 104A, dedicated on-board transmitter 104B, and the inertialnavigation system 104C are depicted together.

The on-board navigation system 104 is configured for computingtime-space-position-information (TSPI) and providing a wireless datalink 106 between the air-based platform 102 and the ground. Thededicated on-board transmitter 104B and the dedicated on-board receiver104A are configured for transmitting and receiving electromagnetic wavesignals through the wireless data link 106. The on-board receiver 104Ais also configured to receive electromagnetic wave signals 118(consisting of signals broadcast by the GNSS space vehicles (SVs) 116,and also navigation and communication signals broadcast by the groundbase pseudolite transmitters 110, also referred to herein as wirelessdata link signals or communication links) broadcast by the GNSS spacevehicles (SV) 116. Separate antennas for receiving the sets ofelectromagnetic wave signals associated with the wireless data link 106and the GNSS space vehicles (SV) 118 may be used but are not explicitlyshown.

A plurality of ground-based receiver nodes 108 are in communication withthe air-based platforms 102 through the wireless data link 106. Theplurality of ground-based receiver nodes 108 are configured to obtaingeolocation measurements from the transmitted electromagnetic wavesignals of the air-based platforms 102 through said wireless data link106. Geolocation solutions may be computed at the processing site, inthis case, at the ground processing station 112. The ground-basedreceiver nodes 108 make signal spectrum measurements and forward themeasurements to the ground processing station 112.

The plurality of ground-based receiver nodes 108 are also configured toreceive signals broadcast from the GNSS SV 116 and use this informationto compute positioning and time synchronization solutions. For example,the ground-based receiver nodes 108 can use this approach to self surveyand self synchronize. Precise location and time synchronization of theground-based receiver nodes 108 and the ground-based pseudolitetransmitter nodes 110 are important for proper operation of the system100. The signals from the pseudolites need to be synchronized and thepseudolite locations also need to be known in order for the pseudolitesystem to provide a PNT capability to the air platform.

The system 100 includes a plurality of ground-based pseudolitetransmitter nodes 110. The ground-based pseudolite transmitter nodes 110are configured to communicate with the on-board navigation system 104,and the dedicated on-board receiver 104A through the wireless data link106. The ground-based pseudolite transmitter nodes 110 are configured tobroadcast communication and navigation signals including controlcommands and navigational messages to the on-board navigation system 104and the dedicated on-board receiver 104A. In some cases the samepseudolite wireless signals used for navigation can also be used tocarry communication information so that separate sets of communicationsignals and navigation signals are not needed.

The system 100 includes at least one ground-based station 112. Theground-based station 112 is a control, monitoring, and processingstation and is in communication with the air-based platforms 102. Aground communication network 114, sometimes referred to as a groundnetwork, is included in the system 100 and is used to transmit andreceive data and messages between the ground-based station 112 and theground-based receiver nodes 108 and ground-based pseudolite transmitternodes 110. The ground communication network may be implemented usingeither hardwired or wireless communications links or a combination ofboth. Thus possible communication links for the ground communicationlinks include, but are not limited to, fiber optic, cable, wire,terrestrial, and non-terrestrial wireless systems, or a combination ofthese. An example of non-terrestrial wireless systems would includeusing a satellite. Satellite systems could be used, for example, toconnect remote locations that do not have a wireless infrastructure.Thus, as depicted in FIG. 1, the ground-based station 112 communicateswith the air-based platforms 102 through the ground communicationnetwork 114, to the ground-based receiver nodes 108, and then from theground-based pseudolite transmitter nodes 110 through the wireless datalink 106 to the air-based platforms.

The ground-based receiver nodes 108 and ground-based pseudolitetransmitter nodes 110 are depicted in FIG. 1 as being co-located, whichis an option. The use of co-located nodes offers some advantagesassociated with position initialization and time synchronization of theground-based pseudolite transmitter 110 nodes by the ground-basedreceiver 108 nodes and simplification of the message and data handlingthrough the network. However, another option is to have the ground-basedreceiver nodes 108 and ground-based pseudolite transmitter nodes 110 bepositioned at different locations (not co-located). The location andpositioning is determined by application-specific conditions, such as,for example, the type of test to be performed or the testingenvironments.

The ground-based station 112 is configured to send control commands toand receive data from the air-based platforms 102, the ground basedreceiver nodes 108, and the ground-based pseudolite transmitter nodes110. For example, the commands could be to initialize or reconfigure theground and air components and the data can include TSPI data as well asstatus and health data of the various components, including identifyingand diagnosing component faults. In the case of remotely correcting afault, the term “reconfigure” corresponds to a more general correctiveaction, which can include a reboot, re-initialization, ortroubleshooting command for further diagnosis.

The ground-based station 112 is configured to monitor and control thecomponents of the on-board navigation system 104 on-board the air-basedplatforms 102, the ground-based receiver nodes 108, and the ground-basedpseudolite transmitter nodes 110. The ground-based station 112 isconfigured to control and monitor the health and status of ground basedreceiver nodes 108, the ground-based pseudolite transmitters 110, andthe on-board navigation system 104. Health monitoring can includeverifying that the commands of the ground-based receiver nodes 108 areexecuted properly and verifying that no component faults or malfunctionshave occurred. Additionally, since the ground-based station 112 is alsoa processing station, it is configured to compute TSPI solutions.

Some embodiments of the invention include a plurality of globalnavigation satellite system space vehicles (GNSS SV) 116 that areconfigured to provide navigation signals to the air-based platforms 102,the plurality of ground-based receiver nodes 108, the ground-basedpseudolite transmitter nodes 110, and the ground-based station 112. Theuse of GPS allows components to synchronize and also for self-surveyingthe ground receiver and pseudolite components.

The navigational signals from the GNSS SV 116 are generically shown asbeing transmitted or broadcast through a wireless downlink signal 118.Receivers would typically process signals from at least four GNSS SV 116in order to compute a PNT solution. Thus, with the inclusion of GNSS SV116, several variations of supplying the control commands and navigationmessages are relevant, including broadcasting the GNSS SV signalnavigation message data bits from the ground-based pseudolitetransmitter nodes 110 to the on-board navigation system 104. This canenable a more robust operation of the on-board navigation systemreceiver 104A in acquiring, tracking and processing the wirelessdownlink signals 118 broadcast from the GNSS SVs 116. Additionally, theground-based receiver nodes 108 self-survey and synchronize by trackingGPS/GNSS SV navigation signals through the wireless downlink signal 118from the GNSS SV 116.

Components designated as “ground-based” in some embodiments are depictedas reference characters 108, 110, 112, 114, and 120. However, withoutloss of generality, the disclosed system and methods may be implementedto provide TSPI solutions for range testing on land, in the open sea,and in littoral zones. Thus, for example, the “ground-based” receivernodes 108, the “ground-based” pseudolite transmitter nodes 110 may bedeployed on buoys and the “ground-based” station 112 can be located on asea vehicle for operation in the open sea or littoral zones. Similarly,the global information grid (GIG) 120, included in some embodiments, isa network that exchanges information (communicates) with theground-based processing station 112 through the ground communicationnetwork 114. As with other components, the GIG 120 may be located onland, in the open sea, and in littoral zones.

In some embodiments, the on-board navigation system 104 includes acomputer (not shown) that is configured to process TSPI and compute theTSPI solutions of the air-based platform 102. The computation isperformed by using the navigation signals from the GNSS SV 116 and thenavigation signals from the plurality of ground-based pseudolitetransmitter nodes 110. When only the GNSS SV signals are available, forexample when the pseudolites are turned off then the on-board navigationsystem 104 can compute TSPI solutions using only the navigation signalsfrom the GNSS SVs 116. When only the navigation signals from theplurality of ground-based pseudolite transmitter nodes 110 areavailable, for example when the GNSS satellite signals are being jammedduring range testing, then the on-board navigation system 104 cancompute TSPI solutions using only the navigation signals from theplurality of ground-based pseudolite transmitter nodes 110.

The dedicated on-board transmitter 104B in the air-based platforms 102is a wireless datalink transmitter configured to transmit the TSPIinformation and monitoring information to the ground-based receivernodes 108. Additionally, the wireless datalink transmitter signal 106transmitted by the on-board transmitter 104B to the ground-basedreceiver nodes, may be a pseudolite type of signal, which issynchronized in time to improve the emitter geolocation operationperformed by the ground-based receiver nodes 108 and the groundprocessing station 112. Synchronized wireless datalink signals 106transmitted by the on-board transmitter 104B could, for example, allowthe use of Time-of-Arrival (TOA) emitter geolocation techniques by theground components rather than Time-Difference-of-Arrival (TDOA) emittergeolocation techniques.

The dedicated on-board receiver 104A in the air-based platforms 102 isconfigured to communicate with the computer (not shown) in the on-boardnavigation system 104. The dedicated on-board receiver 104A isconfigured to receive the navigation signals information from the GNSSSV and the communication and navigation signals information includingcontrol commands and navigational messages from the ground-basedpseudolite transmitter nodes 110. The on-board transmitter 104B isconfigured to receive control information received from the dedicatedon-board receiver 104A sent from the ground-based pseudolite transmitternodes 110 through the wireless datalink signal 106 (or through theon-board computer).

The messages broadcast from the ground-based pseudolite transmitternodes 110 can include a wealth of information. Some of the informationincluded in the messages includes: 1) precise ephemeris and clock dataof the GNSS SVs 116, 2) location and clock data of the ground-basedpseudolite transmitter nodes 110, 3) navigation system controlinformation to initialize or reconfigure components of the on-boardnavigation system 104, 4) GNSS navigation message information configuredfor assisting data stripping navigation message bits on the navigationsignals from the GNSS SVs 116, and 5) GNSS initialization dataconfigured for providing fast acquisition performance. Some of thesemessages enable a higher performance on-board navigation system 104,including: increased navigation accuracy, increased performanceassociated with faster acquisition or reacquisition of the ONSS SV 116signals and higher performance for receiving and tracking GNSS SVsignals in the presence of attenuation or RF interference.

In some embodiments, the ground-based station 112 may include auser-in-the-loop, such as a person carrying a small, mobile computingdevice to control the plurality of ground-based pseudolite transmitter110 nodes and plurality of ground-based receiver 108 nodes and on-boardnavigation system 104, monitor the status of these components anddisplay real-time TSPI information of the air-based platforms 102. Insome embodiments, the ground-based station includes a computer (notshown) configured to process TSPI solutions of the air-based platforms102 using the TSPI information received from the on-board navigationsystem 104 and geolocation measurements received from the ground basedreceiver nodes 108. The ground-based station 112 receives the TSPIinformation from the on-board navigation system 104 via the ground-basedreceiver nodes 108, by way of the ground communication network 114.Similarly, the ground-based station 112 receives the geolocationmeasurements made by the ground-based receiver nodes 108 through theground communication network 114.

Theory of Operation

Reference may sometimes be made, in some embodiments, to “systemcomponents,” or “air-based components,” or “ground-based components” indescribing embodiments of the invention. While variations can exist,“air-based components” generally refer to the air-based platforms 102(sometimes referred to as “air vehicles,” air-based vehicles,” or thelike). However, embodiments described herein can also provide TSPIsolutions for systems that transition through the atmosphere into spacesuch as launch vehicles, rockets, and platforms that operate in theenvironment of space, including space vehicles.

Located on or inside the air vehicle is the on-board navigation systems104, including the dedicated on-board receivers 104A, the dedicatedon-board transmitters 104B, and the inertial navigation system (INS)104C. The GNSS SV 116 can include GPS satellites as well as foreignradio frequency satellite navigation systems, providing navigationsignals indicated by the communication links (118) to the air vehiclesand the ground. The wireless communication link 106 connects theair-based platform with the ground and includes a wireless link from theground-based pseudolite transmitter nodes 110 to the dedicated on-boardreceivers 104A on board the air-based platform 102 and a wirelessdatalink from the dedicated on-board transmitters 104B to theground-based receiver nodes 108.

“Ground-based components” generally refer to the ground-based receivernodes 108, ground-based pseudolite transmitter nodes 110, theground-based station 112 (sometimes also referred to as a control andmonitoring station or ground processing station, or variation thereof),and the ground communication network 114. Additionally, some variationsin number and nomenclature of system components may be made withoutbeing construed as limiting. Some examples include “ground-basedreceiver nodes” 108 & “ground-receivers,” “ground-based pseudolitetransmitter nodes” 110 & “pseudolite transmitters” & simply“pseudolites.”

Other radio navigation systems and signals, sensors and instruments notexplicitly shown in FIG. 1 may likewise be integrated into theground-based, air-based, and space-based components such as, forexample, to enhance the accuracy or robustness of operation underchallenging conditions, such as during range or flight tests involvingGPS jamming. These other navigation systems and signals, sensors andinstruments can include, but are not limited to: Space-BasedAugmentation System (SBAS) signals, LOng RAnge Navigation (LORAN)signals, signals of opportunity, such as signals broadcast fromterrestrial radio and TV stations, and signals transmitted fromcommunications satellites, such as the Iridium satellite system,high-stability frequency standards and clocks, altimeters, compass andother types of navigation aiding sensors and instruments.

Taken together, the ground-based receiver nodes 108 may be referred toas a network of self-surveyed ground receivers (or ground receivernetwork) which are capable of receiving GPS signals (from the GNSS SV116 via the wireless downlink signal 118) to precisely survey theirground-based locations after deployment. This self-survey capabilityallows more rapid deployment and operational cost reduction since amanual survey can be avoided. The ground-based receiver nodes 108 alsoreceive the signals transmitted by the air vehicles 102 via the wirelessdata link 106. Thus, the ground-based receiver nodes (sometimes referredto as a ground receiver network) 108 tracks the GPS signals fromsatellites (GNSS SV 116) and the transmitted data link signal (via thewireless data link 106). The ground-based receiver nodes 108 makemeasurements of the wireless data link signal (via the wireless datalink 106) to geolocate the air platform 102 using Time ofArrival/Frequency of Arrival (TOA/FOA) or Time Difference ofArrival/Frequency Difference of Arrival (TDOA/FDOA) techniques.

The measurements of the wireless data link 106 signal made by theground-based receiver nodes 108 are sent to the ground processingstation 112 using the ground communication network 114. The actualgeolocation solution is computed at the ground processing station 112using TOA/FOA or TDOA/FDOA techniques. The ground-based receiver nodes108 also receive the TSPI information from the on-board navigationsystem 104 transmitted by the on-board transmitter 104B using thewireless data link 106. The TSPI information is also sent to the groundprocessing station 112 using the ground communication network 114.

Directional antenna systems can also make angle-of-arrival (AOA)measurements from the wireless data link signal (via the wireless datalink 106), and AOA measurements made by two geographically displacedsystems can allow triangulation to instantaneously geolocate the airvehicle 102. The AOA measurements would be sent to the ground processingstation 112 using the ground communication network 114, and thetriangulation would normally be performed at the ground processingstation 112. Alternatively, the ground processing station 112 can fusethe AOA information with the TOA/FOA or TDOA/FDOA information and TSPIinformation provided by the on-board navigation system 104 to computemore robust and accurate TSPI solutions of the air-based platform 102.Precise geolocation using AOA techniques generally use large antennas atthe GPS L-band radio frequencies (several meters diameter) whereas smallomni-directional antennas, which are inexpensive and easy to deploy, canbe used for TOA/FOA and TDOA/FDOA techniques.

The transmitted wireless data link signal (via the wireless data link106) includes messages that contain TSPI information generated on-boardby the GPS/INS (104C) navigation system 104, the dedicated on-boardreceiver 104A TSPI information generated by receiving and processing thepseudolite signals transmitted by the ground-based pseudolitetransmitters 110, and possibly data from other sensors. The GPS receivercapability is integrated into the dedicated on-board receiver 104A.

One or more ground-based computers (the ground processing station 112)me networked to the ground-based receivers 108, and perform signalprocessing to fuse the GPS/INS data, the received pseudolite signaldata, and other on-board sensor data with differential GPS correctionsor high-precision GPS ephemeris and clock data to arrive at oneindependent TSPI solution. There are several ways to fuse data to arriveat different variations, depending on the data available and where thefusing is performed. On-board, the received GPS signal data can be fusedwith the INS data to compute TSPI solutions or the aforementioned datacan also be fused on-board with the received pseudolite signal data. Onthe ground, this same data can be further fused with the emittergeolocation measurement data to produce TSPI solutions. The groundprocessing station 112 can be a simple solution, such as, for example, aperson holding a mobile device, like a personal computer (PC), laptopcomputer, or the like or a more complicated solution as computers andequipment deployed within man-made structures.

The GPS/INS data can also utilize the GPS broadcast ephemeris and clockdata to provide a less accurate solution. The GPS receiver can apply theephemeris and clock data it receives directly from the GPS satellites(called “broadcast” ephemeris and clock data) but this data willgenerally be several hours old and, therefore, not as accurate as thenear real-time “precise” GPS ephemeris and clock data. The computers,such as those in the ground-based station 112, also apply the emitterTOA/FOA or TDOA/FDOA) geolocation techniques using the signaltransmitted through the wireless data link 106 to geolocate thetransmitter 104B on the air vehicle 102 to provide another independentTSPI solution. The PC(s) also fuse the aforementioned on-board data withthe emitter geolocation (TOA/FOA or TDOA/FDOA) data to arrive at anotherblended TSPI solution.

Another configuration of embodiments of the invention includespseudolite transmitters 110 (sometimes sometimes simply referred to aspseudolites) at the ground receiver 108 or other locations, and thesignals transmitted by these pseudolites can be received by a modifiedONSS receiver on the air vehicle 102. The pseodolites can bepreferentially located at or near the ground receiver 108 locations soas to have precise GPS coordinates and time available.

The pseodolite signals can provide another independent means of preciseTSPI. In this case, the dedicated on-board receiver 104A of the on-boardnavigation system 104 receives the signals transmitted by a plurality ofground-based pseudolite transmitters 104 to compute TSPI solutionson-board the air platform 102. Or the TSPI information associated withthe pseudolite signals can be transmitted to the ground using thewireless data link 106 signal and the TSPI solutions associated with thepseduolite signals can be computed in the ground processing station 112.The TSPI information associated with the pseduolite signals can be fusedwith other TSPI information in the ground processing station 112, suchas the on-board GPS and INS TSPI information and the emitter geolocationinformation, to generate another alternative and generally more robustand accurate TSPI solution.

Configurations for providing TSPI for multiple air vehicles 102 can usedifferent coded waveforms to isolate or uniquely identify the differentair vehicles, or some other method may be applied for isolation oridentification of multiple air vehicles, such as placing the vehicle IDnumbers in the messages of the wireless data link 106 transmitted byeach vehicle. The ground receiver network 108 would be configured toreceive the GPS signals and also the wireless data link 106 signals fromeach of the multiple air vehicles 102. A way to accomplish thisincludes, for example, having separate tracking channels for each of thewireless data link signals 106, and the ground-based station 112 can beconfigured to compute multiple TSPI solutions for each of the airvehicles 102. Note that the terms ‘ground-based station,” “groundprocessing station,” and the like are often used interchangeably withoutdetracting from the merits or generality of embodiments of theinvention.

The multiple independent TSPI sources of information can also becombined or fused to enable more precise and robust blended TSPIsystems. The data fusing may be done on-board or may be done on theground. The TOA/FOA or TDOA/FDOA emitter geolocation technique using thewireless signal 106 transmitted from the air vehicle 102, wouldtypically be performed on the ground for TSPI applications, and thefusing of the emitter geolocation data with the data measured on-boardthe air vehicle would also be typically performed on the ground. Thewireless data link 106 would be used to transmit the on-board TSPI datato the ground-based receivers 108 and the data would be relayed to theground-based computers/PC(s) (the ground-based station 112) for datafusing, such that the data from the ground based receivers 108 are sentto the ground processing station 112 through the ground communicationnetwork 114.

The ground-based station 112 also fuses the available data to provideblended TSPI solutions. Many algorithms are available for fusing TSPIdata, such as for example, variations of real-time Kalman filters. Somealgorithms may also be applied in post-processing techniques, to furtherimprove the accuracy of TSPI solutions.

The air-based platform 102 also includes a small, low-power transmitter104B to transmit the on-board navigation information to a network ofground-based receivers 108 using a wireless data link signal 106. Thedata link signal 106 may be synchronized to GPS time as computed usingthe on-board GPS receiver 104A (sometimes referred to as “dedicatedon-board receiver” or similar) to provide a precise frequency referenceand time synchronized signal source for application of ground basedTOA/FOA geolocation of the emitter signal such as, for example, thewireless data link 106 signal transmitted from the on-board transmitter104B.

When configured to transmit synchronized GPS-like signals, the dedicatedon-board transmitter 104B is known as a pseudolite, and the dedicatedwireless data link signal 106 signal may be geolocated using TOA/FOAtechniques. Alternatively, when the wireless data link signal 106 cannotbe synchronized to GPS time such as, for example, in the event GPS isdenied when GPS jamming conditions are being tested, then the dedicatedon-board transmitter signal may be geolocated using TDOA/FDOA techniquesin which the time epoch of signal phase transmissions are not exactlyknown. The wireless data link signal 106 messages also include theon-board TSPI information to relay to the ground-based receivers 108.

Multiple wireless data link 106 channels provide further robustness suchas, for example, in the presence of RF interference, and the system caninclude automatic interference monitoring and reconfiguration controlsuch as, for example, switching to a new frequency channel in the eventinterference is detected. In the case of reconfiguration, the dedicatedon-board receivers 104A and the ground-based receivers 108 would becontrolled to correspondingly switch configurations when theground-based pseudolite transmitters 110 and dedicated on-boardtransmitters 104B, respectively, are switched.

The ground-based receiver network 108 receives the GPS satellite signalsand also the dedicated on-board transmitter 104B wireless data linksignals 106. The data link signals 106 transmitted by the dedicatedon-board transmitter 104B and the ground-based pseudolite transmitters110 can be constructed to be OPS-like so as to cause minimalmodification impacts to a traditional GPS receiver, either on-board theair platform or on the ground. Although not specifically differentiatedin FIG. 1, the wireless data link 106 applies to both uplink anddownlink.

The transmitter signal 106 may use a GPS-like pseudorandom nose (PRN)code, may be pulsed, offset in frequency, as in some existing GPSpseudolite designs, so as to cause minimal interference with thereception of GPS signals. Alternatively, the transmitted signal 106 neednot use a GPS-like signal and can use different frequencies and signalcharacteristics. A flexible dedicated on-board receiver 104A andground-based receiver 108 construction can be based on Software DefinedRadio (SDR) for flexible reconfigurations such as, for example, using acombination of Field Programmable Gate Arrays (FPGAs) for high-speedsignal processing functions and PC software for lower-speed signal ordata processing functions. The ground-based receivers 108 may includeprocessing the emitter geolocation signal associated with the wirelessdata link 106 in a tightly-coupled signal processing fashion using theGPS signal for precise timing.

An alternative configuration includes ground-based transmitters 110 thatact as GPS satellites, or pseudolites. These ground-based transmitters110 may be co-located with the OPS ground-based receiver 108 network(sometimes referred to as “nodes”) to facilitate synchronization of thepseudolite signals to the GPS time. The pseudolites 110 can provide anindependent and more robust navigation capability to aid the navigationsystem 104 on-board the air platform 102. For example, the pseudolites110 can provide an independent precise TSPI capability under GPS-deniedconditions. The ground-based pseudolites 110 can be configured withprecise frequency sources and clocks to maintain precise time synch fortesting under GPS-denied conditions.

The ground-based station 112 can include a receiver to receive thenetwork data from the ground-based receivers 108 network, and a computersuch as, for example, a personal computer (PC), or workstation, toprocess the on-board navigation and emitter geolocation data. The groundstation 112 may also include a GPS receiver, such as for example, toprovide time synchronization information. Without loss of generality, aground-based transmitter 110 node and/or a ground-based receiver 112node can be co-located with the ground station 112. In the instance of awired connection, the PC may be a receiver of digital network data. Theground-based station 112 is also connected to the Internet or GlobalInformation Grid (GIG) 120, to receive near real-time, high precisionGPS ephemeris and clock data and other types of data to improve TSPIaccuracy, such as ionospheric corrections, to reduce the GPSsignal-in-space (SIS) errors and thus improve the accuracy of the GPSnavigation solution.

Alternatively, the ground-based receivers 108 network may be configuredto measure local differential GPS corrections or GPS errors, and relaythe errors or corrections to the dedicated on-board navigation system104 or the ground-based station 112 to improve the accuracy of the GPSsolution. The computer in the dedicated on-board navigation system 104or the ground-based station 112 combines the precise ephemeris and clockdata or differential corrections with the TSPI information generatedon-board or transmitted from the air vehicle 102 to the ground receivers108, respectively to provide extremely precise TSPI solutions. Theground-based station 112 also processes the emitter geolocation datareceived from the ground-based receivers 108 network which receive thewireless data link 106 signal to provide another independent solution ofTSPI solutions. The ground-based station 112 may also fuse/combine theTSPI data transmitted from the air vehicle 102 with the emittergeolocation data to provide a blended set of TSPI solutions.

The ground-based station 112 also acts as a remote controlling andmonitoring system for the ground network and the air platformcomponents. For example, the ground-based station 112 can configure theground-based receiver 108 and ground-based pseudolite transmitternetwork 110 and the dedicated on-board receiver 104A and dedicatedon-board transmitter 104B such as, for example, by controlling thefrequencies, waveforms, and other signal characteristics transmitted andreceived by each of the components. In addition, the ground station 112receives status information associated with monitoring the ground andon-board components. This monitoring status information can take theform of the health of components or the configuration status, propercomponent operation or fault information if components are notfunctioning properly. The ground-based station 112 is configured with amission planning feature that is useful for pre-planning the deploymentof the ground network and also to remotely distribute initialization andconfiguration data to and from (and between) the air based and groundbased network of receivers and transmitter nodes. This includesassigning air vehicle ID numbers and vehicle and ground pseudolite PRNcode numbers/IDs, nominal flight trajectory information, time synch,TSPI type, signal processing, and data relay control approach.

Without loss of generality, the proposed system and method may beimplemented to provide TSPI solutions for range testing on land, in theopen sea and in littoral zones. For example, the ground-based receiver108 and ground-based pseudolite transmitter 110 network may bealternatively deployed on buoys and the ground processing station can belocated on a sea vehicle for operation in the open sea or littoralzones. In the case that the ground-based receivers and transmitters arenot stationary, for example located on buoys, the receiver 108 andpseudolite transmitter 110 nodes continuously maintain survey qualityposition, velocity, and time synch information for the system tofunction properly, for example, by the receivers continuously 108processing GPS satellite signals.

More recent advanced techniques for processing data from multiplereceivers may be implemented for improved robustness such as, forexample, techniques associated with collaborative signal processing. Inthis case, receiver measurements may be combined at the raw measurementlevel such that correlator output measurements made by a plurality ofreceivers may be processed in a single filter. This implementationperforms a blended estimation solution of the Position, Velocity andTime (PVT) states of the air platform 102 and other network nodes.

FIGS. 2 and 3 are exemplary block process diagrams/flowcharts, accordingto some embodiments of the invention. Both figures relate to providingtime-space-position-information (TSPI) for air-based platforms using anon-transitory computer-readable medium. Both FIGS. 2 and 3 are equallyapplicable to method and article of manufacture embodiments inconjunction with the system described above and shown on FIG. 1.

Specifically, FIG. 2 depicts the tasks used to plan the deployment anddeploy the physical components and initialize the system and componentsdiscussed above and shown in FIG. 1 in relation to a flight test.Planning the deployment can address such items as how many components todeploy and where to locate the ground components to enable good coverageand wireless data link availability of the air platforms. The deploymentand initialization tasks are depicted as reference character 200.

FIG. 3 depicts the tasks used during the flight test to collect TSPIinformation, depicted as reference character 300, using the systemdescribed and illustrated in FIG. 1. Character 300 in FIG. 3 alsoincludes a final task of collecting the physical components andretrieving the TSPI data. Thus, FIGS. 2 and 3, when taken together,depict the body of tasks performed in using the system disclosed in someembodiments of the invention and illustrated in FIG. 1 for providingTSPI and collecting TSPI information.

Referring to FIGS. 2 and 3 simultaneously, one embodiment of theinvention includes providing time-space-position-information for atleast one air-based platform. This includes providing a system tocollect time-space-position-information (TSPI). The system has at leastone air-based component and a plurality of ground-based components. Aflight test is planned, which includes planning on how to deploy theground components, and then the air-based and ground-based componentsare deployed (Task 202/210). The flight test is then started (Task 302).The air and ground-based components are controlled and monitoredremotely from a ground-based station (Task 304).

System health is monitored (Task 306) as an ongoing task. Additionally,a “system test” can be performed after deployment and initialization andprior to the start of the flight test as this allows correction of anyfaults prior to starting the flight test. Should a problem occur withinthe system, the problem, such as a fault, is diagnosed (Task 308). Adetermination (Task 310) is made whether to fix the problem manually(Task 314) such as, for example, manually repairing a physicalconnection on the ground or to fix the fault by remote command orreconfiguration (task 312) such as, for example, re-booting systemcomponents or re-transmitting commands.

TSPI data is continually collected (Task 316) during the course of theflight test. For example, TSPI data may be collected at rates ofone-Hertz or higher. In the instance of the ground-based stationperforming processing, the TSPI data is sent to the ground-based station(Task 318) and subsequently processed (Task 320) and logged. The TSPIdata is typically stored for post flight analysis. The processed TSPIdata (solutions) is then output and logged. Upon completion of theflight test (determination Task 322), the system components and data arecollected (Task 324). For example, the deployable air-based and groundbased components can be retrieved for use in subsequent tests. Somecomponents may be more permanently installed and not be collected, suchas ground-based networks using hardwired lines.

In yet another embodiment of the invention, a method to obtaintime-space-position-information for at least one air-based platformincludes providing a system having components to collecttime-space-position-information (TSPI). The deployment of the systemcomponents is planned (Task 202). The system components are deployed(Tasks 202/210). The ground network is connected (Task 208). The systemis initialized (parts of Tasks 202 through 216). A flight test isstarted (Task 302).

The system then is remotely monitored (Task 304) to determine systemdiagnostics, which indicates the system health, and faults, if present(Task 306). When it is determined that the system is not functioningproperly (the “no” branch of Task 306), the system problem is diagnosed(Task 308) to determine the cause of the fault. The system problem isfixed either by remote command/reconfiguration or manual repair (Tasks310, 312, 314) and Tasks 304 through 314 are iterated through until thesystem is functioning properly.

Upon verification that that system is functioning properly, the TSPIdata is collected (Task 316) and sent to the processing station (Task318) to process the data (Task 320). Optionally, the TSPI data solutionsmay be output at this point, either as iterative output or final outputwhen the flight test is finished.

Additionally, different types of output can be obtained throughout theprocess such as, for example, system health status output during andafter each of Tasks 306 through 314. A determination is performed toascertain whether the flight test is complete (Task 322). When it isdetermined that the flight test is not complete, tasks 304 through 322are iterated through until it is determined that the flight test iscomplete. Following the completion of the flight test, deployed systemcomponents and data are collected (Task 324). Depending on theoperational environment, some or all of the system components may beleft behind such as, for example, in situations where they may be neededat a later time for a follow-up flight test.

In embodiments, the planning, deployment, and initializing task includestasks 202 through 216. The flight test is planned and the ground-basedcomponents are deployed (Task 202 and 204). The ground-based componentsare self-surveyed to geolocate each of the ground-based components (Task206). This self-surveying function can be accomplished, for example, byeach ground-based receiver node receiving the GPS satellite signals andcomputing their position and time information over an extended timeinterval in order to reduce errors. The ground-based receiver nodes,ground-based pseudolite transmitter nodes, and ground-based station areconnected to the ground communication network (Task 208). The air-basedcomponents are deployed (Task 210). For example, the on-board navigationsystem, including the on-board receiver, transmitter and INS components,may represent a stand-alone system components or payload, which isattached to the air vehicle, inserted into a pod on the air vehicle, orphysically integrated into the air vehicle. The on-board navigationsystem would typically be deployed as a temporary component used duringthe flight test, but may also be permanently integrated on the airvehicle. A determination is made whether the flight test is a GPS-deniedtest or not (Task 212). When the flight test is not a GPS-denied test,the system is remotely initialized and configured to operate using GPS(Task 216) and when a GPS-denied test occurs, the system is remotelyinitialized and configured to operate without using GPS (Task 214).

Articles of Manufacture

Article of manufacture embodiments are directed to non-transitoryprocessor readable medium(s) having stored thereon processor executableinstructions that, when executed by the processor(s), cause theprocessor to perform the process(es) described herein. The termnon-transitory processor readable medium include one or morenon-transitory processor-readable medium (devices, carriers, or media)having stored thereon a plurality of instructions, that, when executedby the electronic processor (typically a central processing unit—anelectronic circuit which executes computer programs, containing aprocessing unit and a control unit), cause the processor toprocess/manipulate/act on data according to the plurality ofinstructions (defined herein using the process/function form). Thenon-transitory medium can be any non-transitory processor readablemedium (media), including, for example, a magnetic storage media,“floppy disk,” CD-ROM, RAM, a PROM, an EPROM, a FLASH-EPROM, any othermemory chip or cartridge, a file server providing access to the programsvia a network transmission line, and a holographic unit. Of course,those skilled in the art will recognize that many modifications may bemade to this configuration without departing from the scope.

In some system embodiments, the electronic processor is co-located withthe processor readable medium. In other system embodiments, theelectronic processor is remotely located from the processor readablemedium. It is noted that the steps/acts/processes described hereinincluding the figures can be interpreted as representing data structuresor sets of instructions for causing the computer readable medium toperform the step/act/process.

Certain embodiments of the invention may take the form of a computerprogram product on a computer-usable storage medium havingcomputer-usable/readable program instructions embodied in the medium.Any suitable computer readable medium may be utilized including eithercomputer readable storage media, such as, for example, hard disk drives,CD-ROMs, optical storage devices, or magnetic storage devices, or atransmission media, such as, for example, those supporting the internetor intranet.

Computer-usable/readable program instructions for carrying outoperations of embodiments of the invention may be written in an objectoriented programming language such as, for example, Python, VisualBasic, or C++. However, computer-usable/readable program instructionsfor carrying out operations of embodiments of the invention may also bewritten in conventional procedural programming languages, such as, forexample, the “C#” programming language or an engineering prototypinglanguage such as, for example, MATLAB®. The computer-usable/readableprogram instructions may execute entirely on the user's computer, partlyon the user's computer, as a stand-alone software package, partly on theuser's computer and partly on a remote computer or entirely on theremote computer. In the latter scenario, the remote computer may beconnected to the user's computer through a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider or any other method known in the art).

Embodiments of the invention are described in part below with referenceto flow chart illustrations and/or block diagrams of methods andcomputer program products according to embodiments of the invention. Itwill be understood that each block of the flow chart illustrationsand/or block diagrams, and combinations of blocks in the flow chartillustrations and/or block diagrams, can be implemented by computerprogram instructions. These computer program instructions may beprovided to a processor of a general purpose computer, special purposecomputer, or other programmable data processing apparatus to produce amachine, such that the instructions, which execute via the processor ofthe computer or other programmable data processing apparatus, createmeans for implementing the functions/acts specified in the flow chartand/or block diagram block or blocks.

These computer program instructions may also be stored in acomputer-readable memory, including RAM, that can direct a computer orother programmable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instructions thatimplement the function/act specified in the flow chart and/or blockdiagram block or blocks.

These computer program instructions may also be loaded onto a computeror other programmable data processing apparatus to cause a series ofoperational tasks to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions that execute on the computer or other programmableapparatus provide tasks for implementing the functions/acts specified inthe flow chart and/or block diagram block or blocks.

In embodiments, the tangible outputs may be shown and/or represented asa visual display screen depiction, hard copy printouts, as well as othermedia using classification/matching information such as, for example, acomputer having computer-readable instructions that is configured to useoutput from embodiments of the invention. The output may be used inprograms using the output such as, for example, in air vehicle sensorperformance evaluation tests or range safety applications.

Demonstration Example

To demonstrate the viability of the use of a small Size, Weight andPower (SWAP) transmitter 104B on-board an air vehicle 102 depicted inembodiments of the invention, the expected wireless data linkperformance is presented assuming a one-Watt on-board transmitter powerat a range of 100 miles. The other on-board components including theon-board receiver 104A and INS 104C can also consist of relatively smallSWAP. The feature of small SWAP is very important for use of theproposed system on SWAP constrained small air vehicles, such as smallUnmanned Air Systems (UAS). The wireless data link 106 performance iscomputed using the link budget equation and other relationships tocalculate predicted bit error rate (BER) as a function ofsignal-to-noise ratio (SNR) or carrier-to-noise density ratio (C/N),assuming omni-directional transmit and receive antenna near GPS L-bendfrequencies, and assuming a 100 Hz bit per second (bps) data rate forrelaying the TSPI information on-board the air vehicle to theground-based receivers 108.

The calculation at an assumed range of 100 miles, wireless propagationpath loss associated with an unobstructed line-of-sight and no otherlosses, provides a C/N of about 55 dB-Hz and an Energy per bit to noiseratio (Eb/N) of about 35 dB for a 100 Hz (20 dB) assumed data rate,which indicates that a BER of 1E-6 can be supported with about a 20 dBlink margin to spare. The extra link margin is important in order toreliably receive the signal when such effects such as signal fading andmultipath are present. Bit error encoding can allow further improvementin the link margin. Assuming precise GPS time synchronization of theground receivers 108, wideband transmitter signals, and a tight couplingof the transmitter and OPS signals, then the time difference of arrival(TDOA) accuracy should be a nanosecond or better, correspondingapproximately to a one-meter geolocation error for good triangulationgeometries. Frequency difference of arrival (FDOA) measurements wouldfurther contribute to the performance. Emitter geolocation error can befurther reduced by averaging over independent samples to reduce theeffects of random error, as the air vehicle 102 moves such as, forexample, by using a Kalman filter. The link margin performance forground based pseudolites 110 transmit power of one-Watt, for the signalbeing transmitted to the on-board receiver 104A, would be comparable.While a one-Watt power consumption enables the use of batteries that mayrepresent a more easily deployable approach in remote areas versus theuse of generators to supply ground power, SWAP constraints for theground-based components may not be as critical as for SWAP constrainedair vehicles. Directional antennas on the ground can be used to enhancelink margin but cause increased complexity and cost since they aregenerally larger than omni antennas and have to be pointed towards theair vehicles 102.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

What is claimed is:
 1. A system for providingtime-space-position-information of an air-based platform in a GPS-deniedenvironment, comprising: at least one air-based platform having anon-board navigation system including a dedicated on-board transmitter,and a dedicated on-board receiver, wherein said on-board navigationsystem is configured for computing time-space-position-information(TSPI) and providing a wireless data link between said air-basedplatform and the ground, wherein said dedicated on-board transmitter andsaid dedicated on-board receiver are configured for transmitting andreceiving signals with navigation information, control commands, andmessages through said wireless data link; a plurality of ground basedreceiver nodes in communication with said at least one air-basedplatform through said wireless data link, said plurality of ground basedreceiver nodes configured to obtain geolocation measurements from saidtransmitted signals of said at least one air-based platform through saidwireless data link; a plurality of ground-based pseudolite transmitternodes in communication with said on-board navigation system, saiddedicated on-board transmitter, and said dedicated on-board receiverthrough said wireless data link, wherein each of said plurality ofground-based pseudolite transmitter nodes are configured to broadcastcommunication and navigation signals including navigation information,control commands, and messages to each of said on-board navigationsystem, and said dedicated on-board receiver; at least one ground-basedstation, wherein said ground-based station is a control, monitoring, andprocessing station is in communication with said at least one air-basedplatform through said wireless data link, said at least one ground-basedstation in communication with each of said plurality of ground basedreceiver nodes and each of said plurality of ground based pseudolitetransmitter nodes through a ground communication network; wherein saidat least one ground-based station is configured to send control commandsto and receive data from said at least one air-based platform, each ofsaid plurality of ground based receiver nodes, and each of saidplurality of ground based pseudolite transmitter nodes; wherein said atleast one ground-based station is configured to monitor and control saidat least one air-based platform, each of said plurality of ground-basedreceiver nodes, and each of said plurality of ground-based pseudolitetransmitter nodes; wherein said at least one ground-based station isconfigured to compute TSPI solutions by using emitter signal geolocationtechniques to geolocate said dedicated on-board transmitter.
 2. Thesystem according to claim 1, wherein said at least one air-basedplatform is selected from the group of air-based platforms consisting ofair vehicles, rockets, launch vehicles, aerostats, space vehicles, andprecision guided munitions.
 3. The system according to claim 1, furthercomprising a plurality of global navigation satellite system spacevehicles (GNSS SV) configured to provide navigation signals to said atleast one air-based platform, said plurality of ground-based receivernodes, said plurality of ground-based pseudolite transmitter nodes, andsaid at least one ground-based station.
 4. The system according to claim3, said on-board navigation system, further comprising: a computerconfigured to process said TSPI and compute said TSPI solutions of saidat least one air-based platform using said navigation signals from saidGNSS SV and said navigation signals from said plurality of ground-basedpseudolite transmitter nodes; wherein said dedicated on-boardtransmitter in said at least one air-based platform is a wirelessdatalink transmitter configured to transmit said TSPI information andmonitoring information to said plurality of ground based receiver nodes;and wherein said dedicated on-board receiver in said at least oneair-based platform is configured to communicate with said computer,wherein said dedicated on-board receiver is configured to receive saidnavigation signals information from said GNSS SV and said communicationand navigation signals information including navigation information,control commands, and messages from said plurality of ground-basedpseudolite transmitter nodes.
 5. The system according to claim 1, saidon-board navigation system, further comprising an inertial navigationsystem integrated with said dedicated on-board receiver.
 6. The systemaccording to claim 4, said navigational messages broadcast from saidplurality of ground-based pseudolite transmitter nodes, furthercomprising precise ephemeris and clock data of said GNSS SV, locationand clock data of said plurality of ground-based pseudolite transmitternodes, navigation system control information for said on-boardnavigation system, GNSS navigation message information configured forassisting data stripping navigation message bits on said navigationsignals from said GNSS SV, and GNSS initialization data configured forproviding fast acquisition performance.
 7. The system according to claim1, wherein said at least one ground-based station is configured tocontrol and monitor the health and status of said plurality of groundbased receivers, said plurality of ground-based pseudolite transmitters,and said on-board navigation system.
 8. The system according to claim 1,said ground-based station, further comprising: a computer configured toprocess TSPI solutions of said at least one air-based platform usingsaid TSPI information received from said on-board navigation system andgeolocation measurements received from said plurality of ground basedreceiver nodes; wherein said ground based station receives said TSPIinformation from said onboard navigation system from said plurality ofground based receiver nodes through said ground communication network;and wherein said ground based station receives said geolocationmeasurements made by said plurality of ground based receiver nodesthrough said ground communication network.
 9. The system according toclaim 1, further comprising a global information grid (GIG) incommunication with said at least one ground-based station.
 10. A methodto provide time-space-position-information for at least one air-basedplatform in a GPS-denied environment, comprising: providing a system tocollect time-space-position-information (TSPI), said system having atleast one air-based component comprising at least one air-basedplatform, said at least one air-based platform having an on-boardnavigation system including a dedicated on-board transmitter, and adedicated on-board receiver, wherein said on-board navigation system isconfigured for computing time-space-position-information (TSPI) andproviding a wireless data link between said air-based platform and theground, wherein said dedicated on-board transmitter and said dedicatedon-board receiver are configured for transmitting and receiving signalswith navigation information, control commands, and messages through saidwireless data link with a dedicated on-board transmitter; a plurality ofground-based components in communication with said at least oneair-based component: planning a flight test and deploying said at leastone air-based component and said plurality of ground-based components;remotely controlling and monitoring said air and ground-based componentsfrom a control and monitoring station; geolocating said on-boardtransmitter using emitter signal geolocating techniques; reconfiguringsaid air and ground-based components when a configuration fault has beendiagnosed; continuing to monitor and control said air and ground-basedcomponents until said flight test is complete; and when said flight testis complete, collecting said time-space-position-information for saidair-based components.
 11. The method according to claim 10, wherein saidat least one air-based platform is selected from the group of air-basedplatforms consisting of air vehicles, rockets, launch vehicles,aerostats, space vehicles, and precision guided munitions.
 12. Themethod according to claim 11, said plurality of ground-based components,comprising: a plurality of ground based receiver nodes in communicationwith said at least one air-based platform through said wireless datalink, said plurality of ground based receiver nodes configured to obtaingeolocation measurements of said at least one air-based platform; aplurality of ground-based pseudolite transmitter nodes in communicationwith said on-board navigation system, and said dedicated on-boardreceiver through said wireless data link, wherein each of said pluralityof ground-based pseudolite transmitter nodes are configured to broadcastcommunication and navigation signals including navigation information,control commands, and messages to each of said on-board navigationsystem, and said dedicated on-board receiver, and wherein said controland monitoring station is at least one ground-based station, whereinsaid ground-based station is a control, monitoring, and processingstation is in communication with said at least one air-based platformthrough said wireless data link, said at least one ground-based stationin communication with each of said plurality of ground based receivernodes and each of said plurality of ground based pseudolite transmitternodes through a ground communication network; wherein said at least oneground-based station is configured to send commands to and receive datafrom said at least one air-based platform, each of said plurality ofground based receiver nodes, and each of said plurality of ground basedpseudolite transmitter nodes; wherein said at least one ground-basedstation is configured to control and monitor the health and status ofsaid plurality of ground based receiver nodes, said plurality ofground-based pseudolite transmitter nodes, said at least one air-basedplatform, and said on-board navigation system; and wherein said at leastone ground-based station is configured to compute TSPI solutions. 13.The method according to claim 12, further comprising: a plurality ofglobal navigation satellite system space vehicles (GNSS SV) configuredto provide navigation signals to said at least one air-based platform,said plurality of ground-based receiver nodes, said plurality ofground-based pseudolite transmitter nodes, and said at least oneground-based station; and a global information grid (GIG) incommunication with said at least one ground-based station.
 14. Themethod according to claim 13, said on-board navigation system, furthercomprising: a computer configured to process said TSPI and compute saidTSPI solutions of said at least one air-based platform using saidnavigation signals from said GNSS SV and said navigation signals fromsaid plurality of ground-based pseudolite transmitter nodes; whereinsaid dedicated on-board transmitter in said at least one air-basedplatform is a wireless data link transmitter configured to transmit saidTSPI information and monitoring information to said plurality of groundbased receiver nodes; and wherein said dedicated on-board receiver insaid at least one air-based platform is configured to communicate withsaid computer, wherein said dedicated on-board receiver is configured toreceive said navigation signals information from said GNSS SV and saidcommunication and navigation signals information including navigationinformation, control commands, and messages from said plurality ofground-based pseudolite transmitter nodes; and an inertial navigationsystem integrated with said dedicated on-board receiver.
 15. The methodaccording to claim 14, said navigational messages broadcast from saidplurality of ground-based pseudolite transmitter nodes, furthercomprising precise ephemeris and clock data of said GNSS SV, locationand clock data of said plurality of ground-based pseudolite transmitternodes, navigation system control information for said on-boardnavigation system, GNSS navigation message information configured forassisting data stripping navigation message bits on said navigationsignals from said GNSS SV, and GNSS initialization data configured forproviding fast acquisition performance.
 16. A method to obtaintime-space-position-information for at least one air-based platform,comprising: (a) providing a system having components to collecttime-space-position-information (TSPI), said system components,comprising: at least one air-based platform having an on-boardnavigation system, a dedicated on-board transmitter, and a dedicatedon-board receiver, wherein said on-board navigation system is configuredfor computing time-space-position-information (TSPI) and providing awireless data link between said air-based platform and the ground,wherein said dedicated on-board transmitter and said dedicated on-boardreceiver are configured for transmitting and receiving signals withnavigation information, control commands, and messages through saidwireless data link, wherein said at least one air-based platform isselected from the group of air-based platforms consisting of airvehicles, rockets, launch vehicles, aerostats, space vehicles, andprecision guided munitions; and a plurality of ground-based componentsin communication with said at least air-based platform; (b) initializingsaid system for a flight test, said initializing task, comprising:determining whether said flight test is a GPS-denied test: when saidflight test is a GPS-denied test, remotely initializing and configuringsaid system to operate without GPS; and when said flight test is not aGPS-denied test, remotely initializing and configuring said system tooperate using GPS; (c) starting said flight test; (d) remotelymonitoring said system to determine system diagnostics, said systemdiagnostics indicating system health; when it is determined that saidsystem is not functioning properly, diagnosing system problem; fixingsystem problem by remote reconfiguration or manual repair and iteratingthrough task (d) until said system is functioning properly; (e)collecting TSPI data when said system is determined to be functioningproperly; (f) sending TSPI data to processing station; (g) processingsaid TSPI data by geolocating said on-board transmitter using emittersignal geolocating techniques, wherein when said flight test is aGPS-denied test, said emitter signal geolocating techniques are selectedfrom time of arrival (TOA) and frequency of arrival (FOA), or timedifference of arrival (TDOA) and frequency difference of arrival (FDOA);(h) determining whether said flight test is complete; when it isdetermined that said flight test is not complete, iterating throughtasks (d) through (h), until it is determined that said flight test iscomplete; (i) collecting said system components and said TSPI data; and(j) outputting said TSPI data in a tangible medium.
 17. The methodaccording to claim 16, said plurality of ground based components,further comprising: a plurality of ground based receiver nodes incommunication with said at least one air-based platform through saidwireless data link, said plurality of ground based receiver nodesconfigured to obtain geolocation measurements of said at least oneair-based platform; a plurality of ground-based pseudolite transmitternodes in communication with said on-board navigation system, and saiddedicated on-board receiver through said wireless data link, whereineach of said plurality of ground-based pseudolite transmitter nodes areconfigured to broadcast communication and navigation signals includingnavigation information, control commands, and messages to each of saidon-board navigation system, said dedicated on-board transmitter, andsaid dedicated on-board receiver; wherein said control and monitoringstation is at least one ground-based station, wherein said ground-basedstation is a control, monitoring, and processing station is incommunication with said at least one air-based platform through saidwireless data link, said at least one ground-based station incommunication with each of said plurality of ground based receiver nodesand each of said plurality of ground based pseudolite transmitter nodesthrough a ground communication network; wherein said at least oneground-based station is configured to send commands to and receive datafrom said at least one air-based platform, each of said plurality ofground based receiver nodes, and each of said plurality of ground basedpseudolite transmitter nodes; wherein said at least one ground-basedstation is configured to control and monitor the health and status ofsaid at least one air-based platform, said plurality of ground-basedreceiver nodes, said plurality of ground-based pseudolite transmitternodes, and said on-board navigation system; and wherein said at leastone ground-based station is configured to compute TSPI solutions. 18.The method according to claim 17, said initializing task, comprising:planning said flight test associated with deploying said plurality ofground-based components based on the flight test planning;self-surveying said plurality of ground-based components to geolocateeach of said plurality of ground-based components; connecting saidplurality of ground based receiver nodes, said plurality of ground-basedpseudolite transmitter nodes, and said at least one ground-basedstation, to said ground communication network; deploying said pluralityof ground-based components; and deploying said at least one air-basedplatform.
 19. The method according to claim 18, further comprising: aplurality of global navigation satellite system space vehicles (GNSS SV)configured to provide navigation signals to said at least one air-basedplatform, said plurality of ground-based receiver nodes, said pluralityof ground-based pseudolite transmitter nodes, and said at least oneground-based station; and a global information grid (GIG) incommunication with said at least one ground-based station.
 20. Themethod according to claim 19, said on-board navigation system, furthercomprising: a computer configured to process said TSPI and compute saidTSPI solutions of said at least one air-based platform using saidnavigation signals from said GNSS SV and said navigation signals fromsaid plurality of ground-based pseudolite transmitter nodes; whereinsaid dedicated on-board transmitter in said at least one air-basedplatform is a wireless data link transmitter configured to transmit saidTSPI information and monitoring information to said plurality of groundbased receiver nodes; and wherein said dedicated on-board receiver insaid at least one air-based platform is configured to communicate withsaid computer, wherein said dedicated on-board receiver is configured toreceive said navigation signals information from said GNSS SV and saidcommunication and navigation signals information including controlcommands and navigational messages from said plurality of ground-basedpseudolite transmitter nodes; an inertial navigation system integratedwith said dedicated on-board receiver; and wherein said navigationalmessages broadcast from said plurality of ground-based pseudolitetransmitter nodes, further comprising precise ephemeris and clock dataof said GNSS SV, location and clock data of said plurality ofground-based pseudolite transmitter nodes, navigation system controlinformation for said on-board navigation system, GNSS navigation messageinformation configured for assisting data stripping navigation messagebits on said navigation signals from said GNSS SV, and GNSSinitialization data configured for providing fast acquisitionperformance.